Since the 19th Century discovery of the cause of cholera epidemics in London and their prevention through treatment of sewage and other effluent to remove and/or kill organisms within the effluent, many advances have been made in the treatment of organically polluted effluent. Early in the development of water treatment systems, chlorine and other halides were found to have deleterious effects on water born organisms, and chlorine compounds are now commonly used to reduce the number of living organisms in water supplies to reasonably safe levels.
It has also been determined that photonic absorption, such as is possible with high levels of radiation at preferentially absorbed frequencies, can cause total photodynamic inactivation of several bacteriophages. (See R. Hall as cited in General Electric Lamp bulletin LD-14; and M. Luckiesh, "Germicidal Eythermal Energy Research" from D. Van Nostrand Co). When a non-fluorescing organism absorbs a photon, the energy is usually converted into vibrational energy (heat) that raises the internal temperature of the organism. Viral organisms are extremely sensitive to such energy. They are so small that the absorption of very few photons causes their internal temperature to rise to levels that are dangerous to their continued existence. In fact, this form of heat energy within viral organisms, causes viral inactivation when the temperatures there within exceed 100.degree. C.
Photobiologists have discovered absorption curves for various biological parts. For example, proteins normally have peak absorption when exposed to radiated ultraviolet (UV) energy at wavelengths of 300 nanometers (nm) to 280 nm, and ribonucleic acid (RNA) has an absorption peak to radiant wavelengths from 265 nm to 245 nm, with an absolute peak at 253.7 nm. The peak absorption for virions occurs at about 260 nm. 184.9 nm energy is the peak energy used for the breakdown of the hydrogen bond that links the DNA chain and phosphorous bond that links the RNA chain. In addition, application of 184.9 nm UV causes free oxygen molecules in the substance under treatment to add an oxygen atom to form ozone, a proven virion deactivator.
Therefore, sterilizers have been constructed that expose a fluid stream to ultraviolet radiation in the 300 nm to 180 nm wavelength range at an applied power of the 30 Kergs per cm.sup.2 or more required to disassociate the deoxyribonucleic acid (DNA) and RNA of viral organisms.
Although with prior art UV sterilization devices, it has been possible to provide UV energy in the correct range of wavelengths and at lethal power levels, such UV devices have had numerous disadvantageous features. First, many have poorly designed flow channels that allow organisms to flow there through without receiving a lethal dose of ultraviolet radiation. Most apply the requisite amount of UV too slowly, thereby allowing viral organisms to produce pigment like molecules that dilute the effect of UV light so that what should be a lethal level, can be withstood. Studies have shown that certain types of viral organisms can produce the UV blocking molecules in as little as ten milliseconds. This means that to apply a lethal dose of UV energy to those virions capable of protecting themselves from UV light, enormous concentrations of UV energy must be provided, since a lethal or at least a debilitating amount of UV energy must be applied and absorbed by every exposed viral organism in less than the first ten milliseconds that the viral organism is exposed. Commercially available intense UV sources used in the prior art devices tend to be narrow frequency devices that are unable to produce lethal intensity at all the peak absorption wavelengths of organisms. The broadband UV energy producing devices that are available produce UV light at relatively low power levels. Examples of these latter sources are UV fluorescent tubes, which produce UV at such low levels that literally hundreds of thousands of lamps are required to treat the effluent in a normal commercial sewage treatment plant.
Over time, when selective kills are attempted, either by chemical means, or inadequate levels or improper wavelengths of radiant energy, microorganisms adapt and become resistant to common killing schemes. Hence, in the case of chlorine, there is evidence that sewer and water supply microorganisms have evolved to tolerate high levels of chlorine. In fact, some now even are able to metabolize chlorine. Not withstanding a reduction in efficacy, chemicals like chlorine build up in an environment, if not poisoning it, changing it in undesirable ways. In addition, chlorination has a high chemical cost, the labor required to monitor that appropriate level of chemicals are present in the water is costly, liability insurance costs are high because the most cost effective means for delivering chlorine involve the use of liquefied chlorine gas which is very hazardous, and the immense cost associated with the removal of the chemical agents from the water prior to discharge cannot be avoided. Hypochlorite powder can be used as a less dangerous chlorine source, but it is five to eight times more expensive than pressurized chlorine. Also, in some third world environments, the water supply is so biologically polluted that so much chlorine has to be added to reduce the organism count to a safe level that the water is no longer safe to use if dechlorination is not done. In fact, at practical dose times and levels of chlorine, some virus are still viable, and protozoan cysts (such as Giardia and Cryptosporidium) and spores of spore forming bacteria are unaffected.
Therefore, there has been a need to provide a non-chemical microorganism sterilization process and device for performing the process that allows less than one viable microorganism (including bacteria, virions, fungi, and bacterial spores) to pass therethrough, which can be manufactured relatively economically, and can operate in highly polluted, organic waste water environments as well as being scalable to portable potable water supplies at one extreme and to large city sewage treatment systems at the other extreme.